This invention relates to an improved process for reacting compounds containing hydroxyl groups with carbodiimides. The improvement lies in the use of Sn(II) and Sn(IV) compounds as catalysts for the addition reaction.
It is known that addition compounds of equivalent quantities of hydroxyl compounds and carbodiimides, particularly, isourea ethers, are valuable textile auxiliaries and useful stabilizers. However, the reaction of alcohols with carbodiimides only takes place under energy-consuming conditions, generally at temperatures above 150.degree. C. Although it is known from German Pat. No. 956,499 that the reaction of carbodiimides with alcohols to form isourea ethers is catalyzed by copper salts, this process has the serious disadvantage that the copper salts give rise to the formation of deep-colored crude products which have to be purified for many applications, in particular, in cases where they are to be used as textile auxiliaries.
Accordingly, the object of the present invention is to find an improved process in which the addition product of carbodiimide and hydroxyl compound may be used for the purposes mentioned above without any need for purification after the reaction.
It has now been found that reaction products of this type particularly isourea ethers and, optionally, their re-arrangement products, may be produced at temperatures as low as 25.degree. to 150.degree. C., provided that the carbodiimide and the hydroxyl compound are reacted in the presence of catalytic quantities of Sn(II) and Sn(IV) compounds. The crude products obtained by the process according to the invention are not colored and may be used without any need for purification. This is of particular advantage in cases where the product formed is a polymeric substance.